59.51.21  :  14.8. 


CONTRIBUTIONS  FROM  THE  ZOOLOGICAL   LABORATORY  Or    I  'IE 

MUSEUM   OF  COMPARATIVE  ZOOLOGY  AT  HARVARD 

COLLEGE.    E.  L.  MARK,  DIRECTOR. 


TH1:    NERVOUS    SYSTEM    OF   TUT;   OKSTODE 
MONE/UA    EXPANSA. 


UC-NRLF 


B    3    3bO    TSfi 


5v   WILLIAM  L    TOWKU. 


TTTH  S       PLATKS. 


REPRINTED  FROM  ZOOU>GISCHK  JAHp.ui:CHK'  .  AP.TH.  F.  ANAT.  u.  ONTOG. 
BAND  XIII.  J'FKI  3. 


CAMBRIDGE,  MA«S.,  U.S.A. 


GIFT  OF 

William  L  Tov/er 


*7  A o T 


BIOLOGY 

RA 
6 


/ 


Nachdruck  verboten. 
Uebersetzungsrecht  vorbehalten. 


The  Nervous  System  in  the  Cestode  Moniezia  expansa. 


Wm.  L.  Tower. 


With  Plates  21—26. 

Contents. 

Introduction. 

I.  Material  and  Methods. 

A.  Material. 

B.  Methods. 

1.  Media  for  Collecting  and 

2.  Keeping  Cestodes  alive  in  the  Laboratory. 

3.  Methods  of  Fixing  and  Staining  the  Nervous  tissues. 
II.  Description  of  the  Nervous  System. 

1.  In  the  Scolex. 

2.  In  the  Neck  Region. 

3.  In  the  Mature  Proglottides. 
Papers   cited. 

Explanation  of  Plates. 

Introduction. 

The  work  of  which  this  is  an  account  was  done  during  the  winter 
of  1895—96.  A  preliminary  paper  was  published  in  the  Zoologischer 
Anzeiger,  July  20,  1896.  It  was  my  intention  at  that  time  to  follow 
the  preliminary  paper  with  a  final  one  as  soon  as  it  could  be  pre- 
pared, but  ill- heath  and  other  circumstances  over  which  I  have  had 
no  control  have  delayed  its  preparation  much  longer  than  I  expected. 

When  this  work  was  begun  the  knowledge  of  the  nervous  system 
in  Cestodes  was  in  a  very  unsatisfactory  condition.  The  anatomy, 
and,  to  some  extent,  the  histology  of  these  forms,  exclusive  of  the 
nervous  system,  were  fairly  well  known.  Considering  the  valuable 

Zool.  Jahrb.  X11L    Abth.  f.  Morph.  24 


36Q  './  :  :/:  •  •  WM.  L.  TOWER, 

i^jjlte  Jobfajfeecl  3by  many  authors  in  using  the  chrome-osmium-silver 
method  blf  UOLGI  and  the  methylen-blue  method  in  neurological  studies 
on  other  animals,  and  the  interesting  character  of  these  worms,  it  is 
rather  surprising  that  the  condition  of  the  nervous  system  should 
have  been  incompletely  determined.  Some  explanation  of  this  may 
be  found,  however,  in  the  seemingly  indifferent  action  of  the  chrome- 
osmium-silver  method  upon  Invertebrates  in  general;  in  the  transient 
character  of  methylen-blue  impregnations;  in  the  loose  arrangement, 
the  non-medullated  character,  and  the  small  size  of  the  nerve  fibres 
of  Cestodes,  which  render  ordinary  stains  useless;  and  in  the  con- 
sequently almost  total  failure  of  the  best  nerve  methods  when  applied 
to  these  parasites.  All  these  conditions  combine  to  make  the  study 
of  the  nervous  system  in  Cestodes  very  difficult. 

From  the  time  of  NIEMIEC'S  (1885)  paper  until  that  of  BLOCH- 
MANN  (1895)  little  or  nothing  had  been  discovered  on  this  subject. 
Previous  to  the  appearance  of  BLOCHMANN'S  paper  the  nervous  system 
of  the  Taenias  had  been  known  to  consist  of  a  system  of  ganglia, 
commissures,  and  connectives  in  the  scolex,  more  or  less  complex, 
according  to  the  species,  as  described  by  NIEMIEC  (1885);  one  large 
and  one  or  two  accessory  lateral  nerve  trunks,  lying  external  to  the 
longitudinal  excretory  tube;  and  two  dorsal  and  two  ventral  nerves 
that  could  not  be  traced  beyond  the  neck  region.  Occasional  branch- 
ings of  these  nerves  in  the  proglottides  had  been  recorded  by  various 
authors,  but  the  course  of  these  branches,  and  the  existence  of  ganglionic 
cells  had  not  been  clearly  demonstrated  in  any  form  until  within  the 
past  two  years.  The  papers  of  BLOCHMANN,  ZERNECKE,  LUHE  and 
COHN,  a  note  by  KOHLER  and  one  by  myself  all  confirm  the  existence 
of  a  constant,  definite  and  extensive  system  of  ganglia,  commissures, 
and  connectives,  a  wealth  of  ganglionic  cells,  and  the  existence  of 
nerve  terminations  in  the  periphery  of  the  animal  that  would  seem  to 
indicate  for  them  a  sensory  function. 

These  results  have  been  obtained  by  the  use  of  three  methods: 
that  of  GOLGI,  the  methylen-blue  intra-vitam  stain ,  and  the  proper 
use  of  VOM  RATH'S  fluid.  In  my  work  I  have  been  only  slightly 
successful  with  methylen-blue,  and  wholly  unsuccessful  with  GOLGI'S 
method;  but  by  the  careful  manipulation  of  the  material  in  VOM 
RATH'S  fluid,  followed  by  crude  pyroligneous  acid,  very  desirable  results 
have  been  obtained.  Many  other  methods  have  been  tried,  but  without 
success. 

Another   and   rather  difficult  problem   constantly  confronted  me 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  361 


during  the  progress  of  my  study  -  that  of  keeping  the- wonns  vaftve 
and  constantly  at  hand  for  use  in  the  laboratory.  $lth0ugh  material 
was  abundant  at  the  abattoir,  it  required  considerable  time 'and  trouble 
to  obtain  it,  and  when  working  with  methylen-blue  it  was  absolutely 
necessary  to  have  a  constant  supply  of  living  material.  As  the 
methods  given  by  LONNBERG  for  this  purpose  were  a  failure,  as  far 
as  this  species  was  concerned,  considerable  time  was  spent  in  ex- 
perimenting with  different  mixtures  and  methods  for  keeping  the 
worms  alive. 

I.     Material  and  Methods. 

A.    Material. 

Abundant  material  from  the  small  intestine  of  Ovis  aries  was 
obtained  as  needed  from  the  abattoirs  of  Boston.  The  cestodes 
Moniezia  expansa  were  taken  from  the  intestines  shortly  after  the 
animals  were  slaughtered  and  before  the  viscera  became  cooled.  It 
was  found  best  to  visit  the  abattoir  early  in  the  morning  soon  after 
work  had  commenced,  as  one  was  then  sure  of  being  able  to  examine 
the  viscera  before  they  became  cool,  or  had  suffered  from  lying  in 
heaps  in  the  "gut  room",  or  from  the  rough  handling  which  often 
destroys  the  larger  and  more  desirable  specimens. 

In  removing  the  worms  it  was  found  undesirable  to  slit  open  the 
intestine,  but  much  better  to  sever  it  near  the  beginning  of  the  coecum, 
then,  beginning  at  the  pylorus,  slowly  to  "strip"  the  intestine  between 
the  thumb  and  forefinger,  causing  the  contents  to  flow  from  the  cut 
end.  In  parasitized  animals  the  greater  number  of  worms  were  found 
in  the  ilium,  or  caudal  portion  of  the  intestine,  a  few  in  the  jejunum, 
and  only  occasionally  one  in  the  duodenal  region.  Although  this 
method  of  removing  the  worms  was  not  all  pleasant,  it  was  rapid  and 
practical.  Moreover,  by  this  method,  the  worms  could  be  removed 
not  only  in  a  more  satisfactory  and  less  broken  condition,  but  more 
easily  and  rapidly,  and  without  exposing  them  to  the  air  as  long  as 
in  the  process  of  opening  the  intestine  longitudinally.  In  almost  every 
case  where  the  worms  were  removed  in  this  manner  the  scolex  came 
away  with  the  proglottides.  Moreover,  the  scolex  was  not  injured  in 
any  way  by  this  treatment,  as  the  worms  evidently  relax  their  hold 
upon  the  intestinal  wall;  whereas,  if  the  intestine  was  slit  open  and 
the  worms  taken  out,  they  invariably  held  tightly  to  the  wall,  and 
could  be  removed  only  by  being  pulled  or  cut  away.  This  resulted 

24* 


362  WM.    L.   TOWER, 

in  'distorting^ 'and   often    tearing  the  scolex  to  such  an  extent  as  to 
:  /•  Oeetidaij  Jit  •  unfit  'v*for  use.    Each  parasitized    animal  usually  contained 
'  from  fw6"*tb  'fifteen   worms,  each  from  50  cm  to  200  cm  in  length, 
and  I  have   occasionally   taken    more   than  fifty  (once  58)  good-sized 
worms  from  one  host. 

B.    Methods. 

1.    Media  for  Collection  and  Transportation. 

The  worms  were  quickly  separated  from  the  contents  of  the  in- 
testines by  the  fingers,  not  with  forceps,  and  placed  in  one  of  several 
media  for  transportation  to  the  laboratory.  For  this  purpose  physio- 
logical salt  solution  (0,75  %)  was  first  used.  This  was  tried  at  various 
temperatures,  from  10°  C  to  30°  C,  but  was  found  to  be  uniformly 
harmful,  as  it  produced  stupefaction  and  rapid  death,  accompanied  by 
a  more  or  less  marked  plasmolysis.  Distilled  water,  faucet  water, 
and  distilled  water  with  sodium  chloride  in  varying  percents  (1  %  to 
6,5%)  were  in  tne  lower  grades  accompanied  by  strong  plasmolysis, 
while  the  higher  percents  acted  as  an  irritating  stimulant,  producing 
distortions  and  death.  If  the  material  was  afterwards  to  be  treated 
with  VOM  RATH'S  mixture,  the  physiological  salt  solution  gave  fair 
results,  provided  the  worms  were  placed  in  his  mixture  as  soon  as 
the  laboratory  was  reached.  It  was  positively  harmful,  however,  to 
allow  the  worms  to  remain  in  this  solution  more  than  one  hour;  for, 
even  after  only  an  hours  exposure,  VOM  RATH'S  method  was  rather 
ineffective,  as  far  as  the  demonstration  of  the  nerves  was  concerned. 
It  would  have  been  more  desirable  to  have  placed  the  worms  in  the 
killing  fluid  at  the  abattoir;  but,  as  all  foreign  substances  had  to  be 
removed  before  killing,  and  this  could  not  be  done  at  the  abattoir,  it 
was  necessary  to  defer  the  killing  until  they  had  been  taken  to  the 
laboratory. 

A  mixture  produced  by  adding  one  percent  of  pepsin  to  normal 
salt  solution  gave  better  results,  as  the  reaction  upon  the  worms  was 
not  as  pronounced  as  that  shown  by  the  physiological  salt  solution. 
With  material  collected  in  this  mixture,  as  also  with  that  in  the 
simple  salt  solution,  I  was  unable  to  obtain  a  satisfactory  intra-vitam 
stain  by  the  methylen-blue  method  or  a  satisfactory  GOLGI  impregnation, 
although  methylen-blue  was  found  to  stain  to  some  extent.  If  the 
amount  of  sodium  chloride  was  decreased  and  that  of  pepsin  increased 
to  the  following  proportions, 


The  nervous  system  in  the  Cestode  Moniezia  ezpansa.  363 

hydrant  water  ....     100,0  ccm 

sodium  chloride    .    .    .        0,5  g 

pepsin      .    ..;..•„  >      1,5  g 

the  results  were  still  more  satisfactory;  but  even  with  material  col- 
lected in  this  mixture  neither  GOLGI  impregnations  nor  methylen-blue 
stains  were  obtained.  When  killed  in  VOM  RATH'S  mixture  material 
collected  in  this  fluid  gave  very  good  results ;  but  the  best  fluid  found 
for  the  transportation  of  the  worms  contained  no  sodium  chloride. 
It  was  composed  of 

hydrant  water    ....    100  ccm 

pepsin 2  g 

egg  albumen  (fresh)     10  to  15  g 

Worms  placed  in  this  mixture  appeared  to  suffer  no  harm  even  if  left  for 
several  hours  provided  the  temperature  did  not  go  delow  10°  C  nor 
above  30°  C.  With  worms  collected  in  this  fluid  a  fair  methylen- 
blue  intra-vitam  stain  was  obtained,  but,  as  my  work  was  nearly  at 
an  end  before  this  solution  was  tried,  I  have  not  been  able  to  test 
it  fully. 

For  all  ordinary  purposes,  preparatory  to  killing  in  the  more 
common  reagents,  I  believe  the  worms  could  be  collected  in  the 
physiological  salt  solution  without  any  appreciable  change  either  in 
cell  arrangement  or  cell  contents;  but  for  the  study  of  nerves  the 
material  should  not  be  placed  in  physiological  salt  solution,  nor  in 
any  solution  containing  sodium  chloride. 

2.    Keeping  Cestodes  Alive  in  the  Laboratory. 

When  the  laboratory  was  reached  the  material  was  first  washed 
or  rinsed  in  the  fluid  in  which  it  was  collected,  or  in  a  fresh  supply 
of  the  same,  until  it  was  free  from  all  dirt  and  chyme.  It  was  then 
placed  in  a  fresh,  clean  portion  of  the  fluid,  and  finally  in  from 
20  to  30  minutes  after  being  taken  from  the  animal,  the  worms  were 
ready  for  the  killing  reagents. 

In  many  cases  it  was  found  desirable  to  keep  the  worms  alive 
for  a  greater  or  less  length  of  time,  especially  when  the  methylen- 
blue  process  was  employed.  Attempts  to  keep  the  worms  in  any 
mixture  containing  salt  were  fruitless,  as  they  could  not  thus  be  made 
to  live  more  than  a  few  hours  at  most.  Distilled  water  and  hydrant 
water  were  both  equally  worthless,  but  after  considerable  experimenting 
and  many  failures  the  following  mixture  was  compounded,  in  which, 


364  WM.   L.   TOWER, 

with  proper  care,  it  was  possible  to  keep  the  worms  alive  for  2, 
3  or  4,  and  sometimes  even  for  5  days: 

hydrant  water     ....     100  ccm 

egg  albumen  (fresh)     .    .      10  g 

pepsin 2  g 

cane  sugar 2  g 

.prepared  beef  (Bo vox) .     .        5  g 

The  worms,  only  one  or  two  in  a  dish,  were  placed  in  this  mixture 
freshly  made,  of  which  100  ccm  was  allowed  to  each  worm.  They 
were  kept  in  the  laboratory  in  the  dark,  no  attention  being  paid  to 
temperature,  for  it  was  found  that  the  temperature  between  certain 
limits  (10°  C  to  30°  C)  was  not  a  very  important  factor,  although 
about  17  °  C  seemed  to  be  the  most  favorable.  Every  morning  the 
worms  were  placed  in  a  freshly  made  mixture,  care  being  taken  to 
clean  thoroughly  the  dishes  before  the  fresh  culture-solution  was  put 
into  them.  I  was  unable  to  use  successfully  the  methods  given  by 
L.ONNBERG  (1892)  for  keeping  Cestodes  alive  in  the  laboratory. 

3.    Methods  of  Fixing  and  Staining  the  Nervous  Tissues. 

The  chrome-osmium-silver  methods  of  GOLGI,  both  the  slow  and 
the  rapid,  with  various  modifications  proposed  by  recent  writers  were 
the  ones  chiefly  tried,  but  always  without  success.  I  was  unable  to 
determine  the  cause  of  failure.  In  nearly  all  cases  there  was,  however, 
a  good  impregnatiou  of  the  dorso-ventral,  longitudinal,  and  transverse 
muscle  fibres.  The  plan  proposed  by  STRONG  (1895)  of  using  formic 
aldehyde  in  place  of  osmic  acid  was  also  unsuccessful,  although  this 
combination  gave  good  results  for  other  Invertebrates  (e.  g.  Echino- 
rhynchus),  used  in  check  experiments. 

Various  modifications  of  the  gold-chloride  methods  were  not  more 
successful  than  the  GOLGI  methods. 

With  the  axis-cylinder  stains  the  results  were  likewise  unsatis- 
factory, although  better  than  with  the  GOLGI  and  gold-chloride  methods. 
The  method  of  NISSL  (1886)  gave  a  good  stain  of  the  lateral  nerve, 
and  by  its  use  many  of  the  other  nerves  could  be  traced  after  one 
had  learned  where  to  look  for  them ;  but  this  stain  did  not  differentiate 
nervous  tissue  from  muscular  and  connective  tissue.  The  method  of 
ALT  (1892)  was  useless  for  my  purpose.  REHM'S  (1892)  method 
was  also  unsatisfactory  in  that  it  did  not  separate  nervous  from 
muscular  and  connective  tissue.  WOLTER'S  method  was  the  most 
satisfactory  for  staining  the  axis  cylinder,  but  it  did  not  dif- 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  365 

ferentiate  nerve  tissues  from  the  other  tissues  as  well  as  VOM  RATH'S 
method. 

Throughout  the  most  of  my  work  material  was  used  that  had 
been  subjected  to  sodium  chloride  solutions,  but  finally  the  solution 
described  on  page  363  was  tried  and  gave  good  results.  Unfortunately 
the  opportunity  was  wanting  for  continuing  the  work  with  this  more 
favorable  material.  The  method  which  at  the  last  was  found  best 
adapted  to  Moniezia  was  as  follows:  The  material  collected  at  the 
abattoir  was  placed  in  the  solution  the  formula  for  which  is  given  on 
page  363,  and  was  thus  carried  to  the  laboratory.  It  was  there 
washed  and  the  worms  not  required  at  once  were  placed  in  the  culture 
solution  described  above  (page  364).  Those  which  were  to  be  treated 
immediately  were  cut  into  pieces  consisting  of  two  or  three  pro- 
glottides  each,  dried  for  a  moment  on  filter  paper,  and  placed  in  a 
clean  watch  glass.  The  pieces  were  then  covered  with  a  freshly  made 
mixture  composed  of  60  and  40  volumes  respectively  of  the  following 
solutions,  A  and  B: 

A.  methylen-blue  (dry)     v;       1  g 
hydrant  water     .    .    .  1000  ccm 

B.  egg  albumen  (fresh)     .      60  g 
hydrant  water     ...      40  ccm 

Only  enough  of  this  mixture  was  used  to  cover  the  specimens,  a  little 
being  added  from   time  to   time  to  replace  that  lost  by  evaporation. 
It  seemed  best  to  keep   the   specimens   exposed   to    the  air  and  at  a 
rather  low  temperature  (3  °  C  to  8  °  C).     After  being  stained  from  half 
an  hour  to  two  hours,  according  to  conditions,  the  material  was  placed 
for  20  or  30  minutes  in  the  following  freshly  made  mixture: 
ammonium  molybdate     .    .    10  ccm 
hydrogen  peroxide      .    »;<v.r      2  ccm 
hydrochloric  acid  (strong)  .      6  drops 

The  object  in  the  use  of  this  mixture  was  to  fix  the  stain  in  the 
nervous  tissues  and  to  wash  it  out  of  all  others ;  but  its  action  in  the 
present  case  shows  that  this  result  does  not  always  follow.  The 
tissues  were  removed  from  the  mixture  as  soon  as  they  became 
greenish,  the  washing  out  having  by  that  time  gone  far  enough.  This 
took  on  an  average  about  half  an  hour,  but  the  time  varied  with  dif- 
ferent specimens.  It  was  best  to  keep  the  mixture  containing  the 
objects  at  a  low  temperature,  near  0°  C.  This  solution  was  then 
gradually  replaced  by  adding  slowly  a  1  °/0  solution  of  osmic  acid  until 
the  ammonium  molybdate  solution  was  replaced  by  a  1  %  solution  of 


366  WM.   L.  TOWER, 

osmic  acid.  The  tissue  was  allowed  to  remain  in  1  %  osmic  acid 
until  it  became  brownish;  it  was  then  removed,  washed  in  50%  al- 
cohol, and  put  into  70%  alcohol  for  twelve  hours.  After  being 
dehydrated  it  was  imbedded  in  paraffine,  xylol  instead  of  chloroform 
being  used  as  a  solvent.  Better  preparations  were  obtained,  however, 
if  the  thoroughly  hardened  material  were  cut  free-hand  in  liver  or 
pith,  cleared  in  xylol,  and  mounted  in  balsam. 

None  of  the  preparations  made  by  this  method,  whether  imbedded 
in  paraffin  or  cut  free-hand,  kept  well.  Those  that  were  good  in 
June  1896  were  of  no  value  a  year  later,  although  they  had  been 
kept  most  of  the  time  in  the  dark,  and  had  never  been  long  exposed 
to  strong  light. 

Trials  with  the  methylen-blue  method  did  not  turn  out  very  suc- 
cessfully until  near  the  end  of  my  work.  I  was  able,  however,  to  get 
some  impregnations,  which,  though  in  themselves  of  little  use,  were 
of  considerable  value  when  taken  in  connection  with  the  results  ob- 
tained by  the  use  of  VOM  RATH'S  method. 

It  was  with  VOM  RATH'S  method  that  the  most  satisfactory 
results  were  obtained.  Although  this  method  does  not  allow  of  the 
isolation  of  the  individual  nerve  elements,  or  neurons,  it  is  admirable 
for  tracing  nerves,  even  when  they  are  small  and  contain  but  a  few 
fibres.  Preparations  made  by  this  method  are  clear  and  well-defined, 
although  not  diagrammatically  so,  like  GOLGI  and  methylen-blue  pre- 
parations. They  also  show  the  histological  structure  of  ganglionic 
cells  better  than  either  of  the  former. 

By  this  method  fair  results  were  obtained  even  when  special 
care  had  not  been  taken  in  collecting  the  material,  but  the  best 
results  were  those  from  material  collected  in  the  solution  described 
on  page  363.  A  fair  staining  of  Moniezia  material  was  also  secured 
with  VOM  RATH'S  mixture  when  the  worms  had  been  collected  in  a 
2%  solution  of  formaldehyde.  Material  left  in  this  solution  35 
days  before  being  placed  in  VOM  RATH'S  fluid  gave  very  fair  results. 
In  this  case  the  stain  was  darker  than  when  fresh  material  was  used, 
but  not  too  dark  to  be  of  considerable  value.  It  is  probable  that 
care  in  regulating  the  exposure  of  such  material  to  the  action  of 
VOM  RATH'S  mixture  would  give  a  lighter  and  more  desirable  stain. 

In  using  VOM  RATH'S  method  fresh  material  was  put  into  the 
following  VOM  RATH'S  mixture: 

sat.  aq.  sol.  picric  acid,  filtered    .    .    500  ccm 
glacial  acetic  acid _,.ftj ,     3  ccm 


The  nervous  system  in  the  Cestode  Moniezia  expansa. 

platinic  chloride  (in  5  ccm  dist.  H2O)     .    5  g 

osmic  acid  crystals 2  g 

After  having  remained  in  this  mixture  for  ten  hours  the  worms  were 
removed  and  cut  into  pieces  from  1  to  3  cm  in  length.  These 
were  put  first  into  crude  pyroligneous  acid  for  from  6  to  10  hours, 
and  then  into  70  %  alcohol  for  24  hours.  After  being  dehydrated  and 
inbedded  in  paraffine  they  were  cut  into  sections  62/3  ^  thick.  This 
method  gave  preparations  in  which  the  nerves  were  colored  grayish 
blue,  the  more  highly  refractive  muscles  brown,  and  the  connective 
tissue  pale  gray  or  steel  blue. 

n.     Description  of  the  Nervous  System. 

A  fresh  adult  specimen  of  Moniezia  expansa  is  commonly  about 
1  m  in  length,  and  from  10  to  15  mm  broad  at  the  posterior  end. 
In  such  an  animal  there  are  between  500  and  1000  proglottides.  The 
scolex  is  on  an  average  1  mm  in  diameter  and  2  mm  in  length, 
measured  from  the  anterior  end  to  a  point  just  posterior  to  the 
cephalic  ganglion;  but  the  dimensions  of  the  scolex  vary  considerably 
in  different  animals.  There  are  neither  rostrum  nor  hooks  in  this  form. 
There  are  two  sets  of  sexual  organs  in  each  proglottis,  opening  one 
on  either  margin  of  the  proglottis  in  a  gonopore.  The  musculature  is 
well  developed  and  is  similar  to  that  found  in  other  Taenias. 

The  anterior  part  of  the  excretory  system  in  the  scolex  of  Mo- 
niezia expansa  consists  of  a  horseshoe-shaped  tube  the  curved  end  of 
which  is  situated  at  about  the  level  of  the  anterior  nerve  ring.  It 
lies  in  the  frontal  plane  and  is  divided  symmetrically  by  the  sagittal 
plane.  Each  of  the  arms  of  this  tube  fork,  giving  rise  to  branches 
that  pass  respectively  dorsal  and  ventral  of  the  cephalic  ganglia 
(PL  21,  Fig.  1).  These  branches  have  been  designated  as  the  dextro- 
dorsal,  va.  dx-d;  the  dextro- ventral,  va.dx-v\  the  sinistro-dorsal,  va.s-d, 
and  the  sinistro- ventral  longitudinal  excretory  tubes  (PI.  21,  Figs.  1, 
5  and  6).  These  four  tubes  bend  slightly  outward  (PL  21,  Fig.  1), 
passing  close  to  the  surface  of  the  cephalic  ganglia,  opposite  which 
they  turn  sharply  outward  and  forward;  but,  after  continuing  for  a 
short  distance  in  this  direction,  they  turn  backward  through  an  angle 
of  more  than  90  °,  and  run  parallel  to  one  another  and  to  the  lateral 
nerve.  These  four  excretory  tubes  pass  backward  through  the  neck 
region  into  the  younger  proglottides,  the  dorsal  pair  becoming  larger 
and  occupying  the  position  of  the  longitudinal  excretory  tubes  of  the 


368  WM.   L.   TOWER, 

mature  proglottides ,   while  the  ventral   pair   becomes  smaller  and  is 
lost  in  the  older  proglottides. 

The  nervous  system  of  Monieeia  is  imbedded  in  the  connective 
tissue  of  the  body  without  any  definite  bounding  membrane  or 
continuous  protective  structure.  Many  of  the  larger  and  more  im- 
portant trunks,  however,  have  along  their  courses  cells  (cl.viri)  of  a 
peculiar  character.  They  are  elliptical,  about  twice  as  long  and  half 
as  thick  as  they  are  broad,  and  from  each  cell  there  are  given  off  a 
number  of  branching  processes  that  run  over  the  surface  of  the  nerve. 
I  believe  that  these  processes  serve  to  bind  the  nerve  elements  into 
a  firmer  structure,  though  they  are  not  very  close  together,  and  do 
not  form  a  continuous  covering.  These  ("binding  cells")  are  shown  in 
PL  24,  Figs.  15  and  16;  PL  25,  Figs.  29  and  30,  and  are  somewhat 
different  from  the  Hiillzellen  described  by  ZERNECKE  (1895,  p.  137)  from 
Ligula.  They  occur  upon  the  nerves  of  the  scolex  and  upon  the  large 
lateral  nerve  trunks.  I  have  not  yet  found  them  upon  the  other  nerves. 

1.    In  the  Scolex. 

The  nervous  apparatus  of  the  scolex  consists  of  1)  the  anterior 
nerve  ring  with  its  four  ganglia ;  2)  the  pair  of  large  cephalic  ganglia ; 
3)  the  connecting  bundles  of  nerves  between  1  and  2  and  4)  the  dorsal 
and  ventral  commissures  connecting  the  outer  ends  of  the  cephalic 
ganglia. 

At  about  one-fifth  of  the  length  of  the  scolex  from  its  anterior 
end  is  found  that  part  of  the  central  nervous  system  which  I  have 
called  the  anterior  nerve  ring  (n.a,  PL  21,  Fig.  1).  The  ring  contains 
four  ganglia,  one  in  each  of  the  four  quadrants  formed  by  the 
intersection  of  the  sagittal  and  lateral  planes  of  the  scolex,  and  a 
little  in  front  of  and  deeper  than  the  corresponding  acetabulum. 
These  ganglia  are  here  designated  according  to  their  positions  as  the 
anterior  dextro-dorsal  (gn.a.dx~d,  PL  21,  Fig.  1),  sinistro-dorsal 
(gn.a.s-d),  dextro-ventral  and  sinistro- ventral  ganglia.  The  bundles 
of  nerve  fibres  connecting  the  ganglia  with  one  another  constitute  the 
anterior  nerve  ring.  The  ganglia  contain  a  moderate  number  of 
ganglionic  cells,  which  differ  from  those  of  the  rest  of  the  nervous 
system  in  size.  They  are  small  and,  I  believe,  mostly  unipolar, 
although  there  are  a  few  bipolar  and  multipolar  ones.  These  cells 
(PL  24,  Figs.  21—24,  26)  have  a  clear  and  relatively  large  nucleus,  with 
a  deeply  staining  nucleolus;  but  no  trace  of  a  chromatin  network  or 
granular  structure  was  observable  in  the  nucleoplasm.  The  nuclear 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  369 

membrane  is  very  thin,  often  almost  indistinguishable  from  the 
granular  cytoplasm  that  surrounds  the  nucleus,  but  it  is  not  of  uniform 
thickness,  small  thickenings  appearing  without  regular  arrangement 
upon  its  inner  surface.  The  cytoplasmic  contents  are  gathered  about 
the  nucleus  into  a  dense  granular  mass,  from  which  threads  and  films 
of  spongioplasm  radiate  through  the  hyaloplasm  to  the  cell  wall,  thus 
producing  more  or  less  of  a  stellate  appearance  (PI.  24,  Figs.  2 1—24,26). 
From  these  anterior  ganglia  are  given  off  nerve  fibres  that  are  distri- 
buted to  the  anterior  end  of  the  scolex,  to  the  acetabula,  and  to  the 
musculature  of  that  region.  I  was  not  able  to  discover  any  regularity 
in  the  number  or  distribution  of  these  branches,  such  as  NIEMIEC  (1885) 
has  shown;  there  was  instead  a  very  loose,  poorly  defined,  set  of 
nerves  that  crossed  and  recrossed  one  another  in  a  very  confusing 
manner. 

NIEMIEC  (1885)  has  described  in  Taenia  coenurus  a  nerve  ring 
lying  anterior  to  the  acetabula,  but  having  eight  ganglia  --  instead 
of  four,  as  in  Moniezia  -  -  placed  in  pairs,  one  pair  in  each  quadrant 
of  the  scolex.  In  Taenia  serrata  he  also  found  an  anterior  nerve 
ring,  but  without  any  pronounced  ganglionic  enlargements. 

In  Moniezia  expansa,  as  in  Taenia  coenurus,  there  are  eight 
distinct  longitudinal  nerve  trunks  that  pass  backward  from  the  anterior 
nerve  ring,  two  arising  in  each  quadrant  of  the  ring,  but  unlike  Taenia 
coenurus  these  large  pairs  of  nerve  trunks  have  their  origin  in  the 
posterior  surface  of  each  of  the  four  anterior  ganglia,  one  on  the  ex- 
ternal edge  of  the  ganglion,  the  other  on  its  internal  edge.  The  one 
arising  on  the  inner  edge  which  is  the  larger,  passes  to  the  cephalic 
ganglion  of  its  own  side,  and  in  passing  backward  approaches 
toward  the  chief  axis  of  the  worm ;  while  the  one  that  arises  from 
the  outer  edge  runs  posteriorly  parallel  to  the  surface,  becoming 
either  one  of  the  two  dorsal  or  two  ventral  longitudinal  nerves.  (The 
further  description  of  these  outer  nerves  will  be  taken  up  after  an 
account  of  the  inner  nerves  and  of  the  position  of  the  nervous  apparatus 
immediately  connected  with  them.) 

The  two  inner  nerves  arising  from  the  ganglia  of  the  right  side 
of  the  animal  converge  until  they  meet  at  a  point  not  far  behind  the 
division  of  the  excretory  tube  into  its  dorsal  and  ventral  branches, 
where  they  at  the  same  time  unite  with  the  right  anterior  horn  of 
the  cephalic  ganglion  (PL  21,  Figs.  1  and  2).  The  nerves  of  the  left 
side  have  similar  relations.  These  nerves  may  be  called  the  cephalic 
connectives,  being  simply  compact  bundles  of  nerve  fibres  without 


370  WM.    L.   TOWER, 

ganglionic  cells  or  any  of  the  protecting  or  "binding"  cells  charac- 
teristic of  other  portions  of  the  nervous  system.  They  do  not  give 
off  branches  in  any  part  of  their  entire  length,  but  are  simply  con- 
nectives between  the  anterior  ganglia  and  the  main  portion  of  the 
central  nervous  system  -  -  the  pair  of  large  cephalic  ganglia. 

The  large  cephalic  ganglia  are  situated  in  the  posterior  part  of 
the  scolex,  a  little  behind  the  acetabula,  one  on  each  side  of  the 
sagittal  plane.  Each  of  these  cephalic  ganglia  consists  of  a  large 
rounded  mass  or  body  (compare  PI.  21,  Figs.  1  and  5,  and  PL  22, 
Fig.  8)  with  a  fairly  smooth  even  surface  and  two  projections  or 
horns.  The  anterior  median  side  of  each  is  prolonged  anteriorally 
into  a  conical  process,  the  anterior  horn  (PI.  22,  Fig.  8  conu.  a),  which 
receives  the  fibres  of  the  cephalic  connectives  of  its  own  side.  The 
lateral  portion  of  each  ganglion  is  also  prolonged  into  a  cone-shaped 
structure,  the  external  horn  (conu. ex),  which  contains  the  fibres  of 
the  lateral  nerve.  The  two  ganglia  are  connected  with  each  other 
by  a  relatively  small  commissure  (PL  22,  Fig.  8  corns),  the  fissure 
between  the  ganglia  in  the  median  plane  being  deep,  especially  in 
front  and  behind. 

The  body  of  the  cephalic  ganglion  is  made  up  of  a  core  of 
ganglionic  cells  traversed  by  nerve  fibres  and  a  cortical  portion  com- 
posed almost  entirely  of  fibres,  the  whole  being  enveloped  in  the 
richly  branched  "binding"  cells.  The  ganglionic  cells  are  not  as  large 
as  those  in  the  ganglia  of  the  proglottides ,  but  they  are  like  them 
in  every  other  respect.  Many  of  them  are  multipolar,  and  are  often 
richly  supplied  with  branching  processes  (PL  24,  Fig.  18).  The  nuclei 
are  relatively  large,  spherical,  hyaline,  with  a  deeply  staining  nucleolus 
but  no  chromatic  network ;  the  nuclear  membrane  is  thin,  has  irregular, 
thickened  places,  and  in  some  instances  a  shrunken  appearance,  very 
much  like  that  found  by  HODGE  (1892)  in  the  spinal  ganglia  of  Verte- 
brates after  a  day's  exercise,  or  after  artificial  stimulation.  In  the 
cell  shown  in  PL  24,  Fig.  18  the  dendritic  or  protoplasmic  processes 
are  very  numerous,  but  in  VOM  RATH  preparations  they  are  not  easily 
followed.  Some  of  the  nerve  processes  of  such  ganglionic  cells  have 
deeply  staining  thickenings  occurring  at  about  equal  intervals,  as 
may  be  seen  in  some  of  the  processes  of  Fig.  18.  Bipolar  cells  are 
much  more  common  than  those  of  the  unipolar  type,  and  occasionally 
there  is  found  a  peculiar  form  (PL  24,  Fig.  19),  which  might  readily 
be  taken  for  a  unipolar  cell,  but  which  is  in  reality  bipolar.  The 
cytoplasmic  contents  of  these  cells  have  the  same  stellate  arrangement 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  37  ^ 

as  in  the  other  ganglionic  cells  of  this  animal.  Where  the  nerve  fibre 
joins  the  cell  there  is  an  accumulation  of  granules  similar  to  that 
about  the  nucleus  (PL  24,  Fig.  18).  The  anterior  and  external  horns 
of  the  cephalic  ganglia  have  but  few  ganglionic  cells,  being  for  the 
most  part  composed  of  nerve  fibres. 

Although  I  am  not  yet  prepared  to  give  a  detailed  account  of 
the  path  taken  by  the  nerve  fibres  through  the  cephalic  ganglion,  I 
have  to  some  extent  followed  their  courses  and  give  what  I  believe 
to  be  the  paths  of  the  principal  groups  of  them.  There  is  a  large 
bundle  of  fibres  (PI.  22,  Fig.  8  B\  which  seems  to  arise  from  the 
central  ganglionic  mass  of  either  side,  and  to  pass  through  the  posterior 
part  of  the  transverse  commissure  into  the  ganglion  of  the  opposite 
side.  The  bundle  here  traverses  the  posterior  part  of  the  ganglion, 
curving  around  behind  the  ganglionic  core,  and  emerges  through  the 
external  horn  to  enter  the  lateral  nerve  of  the  side  opposite  that  in 
which  it  arose.  This  bundle  is  joined  just  before  it  passes  through 
the  transverse  commissure,  by  a  smaller  bundle  (PL  22,  Fig.  8  D), 
which  enters  the  cephalic  ganglion  through  its  anterior  horn,  probably 
arising  from  the  two  "anterior  ganglia"  of  the  same  side  of  the  scolex. 
A  third  bundle  of  fibres  arising  from  the  anterior  ganglia  of  each 
side  enters  the  cephalic  ganglion  of  the  same  side  through  its  anterior 
horn,  passes  along  the  anterior  border  of  this  ganglion  near  its  sur- 
face and  finally  emerges  through  its  external  horn  to  enter  the  lateral 
nerve  of  the  same  side  of  the  scolex  in  which  it  originated.  There 
are  also  several  other  smaller  distinct  bundles  of  nerve  fibres  in  the 
body  of  the  cephalic  ganglia,  the  most  conspicuous  one  being  a  bundle 
that  traverses  the  anterior  part  of  the  transverse  commissure  con- 
necting the  central  ganglionic  cells  of  one  cephalic  ganglion  with 
those  of  the  other. 

The  external  horn  of  the  cephalic  ganglion  is  enlarged  where  it 
joins  the  lateral  nerve,  and  from  this  enlargement  arise  several  small 
nerves  that  are  distributed  to  the  acetabula  and  to  the  muscles  that 
operate  them.  From  this  enlargement  there  also  arise  two  broad 
bands  of  nervous  tissue,  one  from  its  dorsal,  the  other  from  its 
ventral  surface.  The  former  passes  dorsad  of  the  dorsal  excretory 
tubes,  the  latter  ventrad  of  the  ventral  excretory  tubes,  to  enter  the 
corresponding  regions  of  the  cephalic  ganglion  of  the  opposite  side 
of  the  body.  These  are  respectively  the  dorsal  and  ventral  cephalic 
commissures  (PL  21,  Figs.  1  and  5  corns,  d',  corns,  v').  These  com- 
missures are  thin  bands  of  loosely  arranged  nerve  fibres,  which  in 


372  WM.    L.    TOWER, 

their  course  meet  the  two  dorsal  and  two  ventral  longitudinal  nerves. 
Not  only  do  fibres  of  these  bands  decussate  with  those  of  the  longi- 
tudinal nerves,  but  fibres  also  pass  from  commissure  to  longitudinal 
nerve  and  vice  versa.  Along  the  course  of  these  commissures  there  are 
found  a  few  ganglionic  cells  which  are  mostly  of  the  unipolar  type  (PL  22, 
Fig.  11).  The  position  and  appearance  of  these  commissures  reminds 
one  of  the  two  hexagonal  commissures  found  by  NIEMIEG  (1885)  in 
Taenia  coenurus  and  T.  serrala,  with  one  of  which  they  are  pro- 
bably homologous,  although  apparently  they  are  less  well  defined 
nerves  than  those  in  the  species  studied  by  NIEMIEC. 

Returning  to  the  four  outer  nerves  arising  from  the  anterior 
ganglia,  it  is  found  that  in  running  backward  they  approach  one 
another  slightly  and  that  each  passes  through  the  dorsal  or  ventral 
cephalic  commissure,  from  which  a  few  nerve  fibres  are  received. 
Behind  the  cephalic  commissure  they  run  nearly  parallel  with  one 
another,  becoming  the  dextro-dorsal,  sin istro- dorsal,  dextro-ventral 
and  sinistro-ventral  longitudinal  nerves  (PI.  21,  Figs.  1,  2,  4  and  5). 
In  the  scolex  these  are  simple,  rather  compact  bundles  of  nerves, 
without  ganglionic  or  ubinding"  cells;  but  in  passing  backward 
ganglionic  cells  begin  to  appear  in  the  neck  region.  At  first  these 
are  few,  but  as  older  proglottides  are  reached  the  number  increases. 
These  nerves  correspond  exactly  in  origin,  position  and  the  course 
taken  with  those  described  by  NIEMIEC  (1885)  in  Taenia  coenurus 
and  T.  serrata.  NIEMIEC  was  unable  to  trace  them  beyond  the  neck 
region,  but  I  have  found  them  in  proglottides  taken  from  all  parts 
of  the  worm,  and  always  occupying  the  same  relative  position  in  the 
proglottis.  Although  I  have  not  traced  them  continuously  from  pro- 
glottis  to  proglottis  through  an  entire  strobila,  I  think  that  their  occur- 
rence in  the  same  relative  position  in  proglottides  taken  at  random 
in  the  same  animal  is  evidence  enough  that  they  are  continuous 
throughout  the  entire  length  of  the  worm. 

2.    In  the  Neck  Region. 

In  the  neck  region  of  Monieza  the  most  prominent  nerves  are 
the  six  longitudinal  ones.  The  two  large  lateral  nerves  arising  from 
the  external  horns  of  the  cephalic  ganglia  lie  in  the  usual  position 
external  to  the  longitudinal  excretory  tube.  They  are  single  nerve 
trunks  nearly  circular  in  cross-section,  and  not  sharply  defined  in 
outline.  I  have  not  succeeded  in  finding  in  Moniesia  the  two  ac- 
cessory lateral  nerves  which  are  described  for  other  forms  by  NIEMIEC, 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  373 

and  COHN,  as  accompanying  each  of  the  lateral  nerve  trunks. 
For  the  first  5  mm  behind  the  scolex  the  lateral  nerves  are  of  uni- 
form diameter,  they  possess  only  a  few  ganglionic  cells  and  no  trace 
of  ganglionic  enlargements.  The  "binding"  cells  enveloping  them  are 
few,  long  tracts  existing  without  any  such  elements.  The  branches 
arising  from  the  lateral  nerves  are  mostly  limited  to  the  formation  of 
the  dorsal  and  ventral  commissures  (PI.  21,  Fig.  1). 

The  dorsal  and  ventral  nerves  are  likewise  without  ganglionic 
enlargements  in  the  neck  region,  and  the  ganglionic  cells  are  few.  In 
the  posterior  part  of  the  neck  region  where  the  proglottides  begin  to 
be  distinguishable,  the  nerves  begin  to  assume  the  condition  which 
they  present  in  the  mature  segments.  In  this  portion  of  the  neck 
region  each  lateral  nerve  begins  to  exhibit  an  enlargement  at  a  point 
near  the  posterior  margin  of  the  proglottis.  This  enlargement  is  due 
to  the  increased  number  of  ganglionic  cells  occurring  in  the  nerve  at 
that  point ;  these  increase  in  number  continuously  until  the  proglottis 
is  mature.  The  enlargement  of  the  lateral  nerve  caused  by  this  in- 
crease in  the  number  and  size  of  the  ganglionic  cells  is  the  first  in- 
dication of  the  posterior  lateral  ganglion  (PL  21,  Fig.  1  gn.l.p).  The 
position  of  these  ganglia  is  indicated  in  the  preceding  portion  of  the 
neck  region  by  the  presence  of  the  small  branches  from  the  lateral 
nerve  which  correspond  in  position  to  the  posterior  part  of  each  young 
proglottis.  These  branches  are  undoubtedly  the  beginnings  of  the 
dorsal  and  ventral  commissures  of  the  mature  segments  which  are 
recognizable,  then,  before  the  ganglionic  enlargements  of  the  lateral 
nerve  with  which  they  are  connected. 

At  a  distance  of  30  mm  from  the  scolex  the  posterior  lateral 
ganglia  are  well  marked.  In  favorable  sections  from  this  region  made 
in  a  frontal  plane  it  is  possible  to  trace  the  individual  neurons  of 
the  lateral  nerves  (PL  26,  Fig.  32).  The  ganglionic  cells  are  usually 
nearly  triangular  and  of  the  unipolar  type ;  there  are  a  great  number 
of  dendritic,  or  protoplasmic,  processes  which  interlace  with  those  of 
neighboring  ganglionic  cells.  In  the  section  shown  in  PL  26,  Fig.  32, 
there  are  three  unipolar  and  two  bipolar  ganglionic  cells,  which,  for 
some  reason,  are  more  deeply  stained  than  the  others.  At  least  two 
kinds  of  neurons  are  distinguishable ;  in  one  the  ganglionic  cell  sends 
a  nerve  fibre  posteriorly  from  its  ganglion  to  the  next  following  one ; 
in  the  other  anteriorly  to  the  preceding  ganglion.  A  complete  iso- 
lated neuron  is  shown  in  PL  24,  Fig.  25. 

In    each   of  the   ganglionic   enlargements   there   lie  between  the 


374  WM.  L.   TOWER, 

ganglionic  cells  others  which  do  not  appear  to  have  any  nerve  fibre 
connected  with  them.  These  cells  are  richly  branched,  the  branches 
interlacing  with  the  dentritic  processes  of  the  ganglionic  cells.  It  is 
impossible  to  say  whether  they  act  as  a  means  of  connection  between 
different  neurons,  whether  they  are  developing  ganglionic  cells,  or  have 
some  other  function.  One  of  these  cells  is  shown  very  faintly  in 
PI.  26,  Fig.  32.  In  this  region  the  dorsal  and  ventral  commissures 
have  become  in  so  far  complete  that  they  can  be  traced  from  the 
posterior  lateral  ganglion  of  one  side  to  that  of  the  other.  The 
ganglia  of  the  dorsal  and  ventral  nerves  have  also  begun  to  be 
distinguishable,  but  there  is  as  yet  no  trace  of  the  anterior  lateral 
ganglion,  nor  of  the  genital  or  marginal  nerves.  At  least  it  has  not 
been  possible  by  any  method  which  I  have  used  to  demonstrate  their 
presence  until  after  the  dorsal  and  ventral  commissures,  as  well  as 
the  dorsal  and  ventral  ganglia,  have  made  their  appearance. 

3.    In  the  Mature  Proglottis. 

In  each  lateral  half  of  every  proglottis  there  is,  besides  the 
dorsal  and  the  ventral  commissures  and  the  large  lateral  nerve,  a 
dorsal  and  a  ventral  longitudinal  nerve,  an  internal  and  an  external 
genital  nerve,  and  a  marginal  nerve.  The  lateral  nerve  trunk  is  im- 
bedded in  the  parenchyma  of  the  body,  from  which  it  is  not  sharply 
defined;  it  is  elliptical  in  cross-section,  the  larger  axis  of  the  ellipse 
having  a  dorso-ventral  direction.  The  course  of  these  nerves  is  nearly 
parallel  to  that  of  the  longitudinal  excretory  tube  (PL  22,  Fig.  6  n.  I). 
The  nerve  is  a  compact  bundle  of  naked  axis  cylinders  separated 
from  one  another  by  a  structureless  hyaline  matrix,  the  whole  being 
bound  together  by  peculiar  binding  or  protecting  cells  like  those  found 
in  the  scolex.  These  cells  appear  elliptical  in  outline,  and  send  out 
a  considerable  number  of  branching  processes  that  run  over  the  sur- 
face of  the  nerve,  and  serve,  I  believe,  to  bind  the  nerve  fibres  into 
a  compact  bundle  and  to  separate  them  in  a  measure  from  the  tissues 
in  which  the  nerve  is  imbedded  (PL  25,  Fig.  30-c?.vm).  These 
branches  are  not,  however,  so  numerous  nor  so  dendritic  in  character 
as  in  the  cells  of  similar  function  figured  by  ZERNECKE  (1896,  tab.  13, 
figs.  55, 56)  for  Ligula.  In  longitudinal  sections  of  the  nerve  they  appear 
lenticular,  the  edges  being  prolonged  for  a  considerable  distance  over 
the  surface  of  the  nerve  trunk.  In  some  regions  they  lie  singly,  separated 
from  each  other  by  a  considerable  distance;  in  others  they  lie  close 
together,  as  seen  in  Figs.  9  (PL  22)  and  15  (PL  24).  There  seems  to  be  no 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  375 

regularity  as  to  their  arrangement.  In  VOM  RATH  preparations  the 
nuclei  of  some  of  these  cells  are  deeply  stained  and  each  contains  a 
very  dense  nucleolus  (vin.d,  PL  25,  Fig.  29  and  PL  24,  Fig.  15); 
whereas,  in  other  binding  cells  of  the  same  preparation  the  nucleus 
is  unstained,  while  the  nucleolus  is  deeply  stained.  Granular  cyto- 
plasm is  usually  collected  around  the  nucleus  and  passes  thence  in 
radiating  and  sometimes  branching  strands  to  the  periphery  of  the 
cell,  giving  the  whole  a  stellate  appearance.  These  are  probably 
modified  mesodermal  cells. 

Along  the  course  of  the  lateral  nerve  between  the  anterior  and 
posterior  lateral  ganglia  there  are  ganglionic  cells,  some  of  them  in 
the  nerve  itself  others  outside  the  nerve.  These  ganglionic  cells  are 
mostly  bipolar  or  multipolar,  but  in  one  case  (PL  25,  Fig.  30  cl.gn), 
two  unipolar  ganglionic  cells  were  found  lying  outside  the  nerve  and 
sending  each  an  axis  cylinder  into  the  nerve.  In  one  case  the  fibre 
shortly  left  the  nerve,  and,  passing  outward,  terminated  in  a  cup- 
shaped  structure,  which  enveloped  one  end  of  an  ellipsoidal,  hyaline, 
structureless  body,  the  other  end  of  which  was  enveloped  by  a  similar 
cup-shaped  structure  formed  by  the  end  of  another  nerve.  I  have 
observed  this  structure  in  several  methylen-blue  preparations,  however 
I  am  inclined  to  believe  that  it  is  due  to  some  post-mortem  change 
caused  by  the  reagents  used.  The  ganglionic  cells  which  lie  in  the 
nerve  substance  (PL  24,  Fig.  15  cl.gri)  are  usually  small  and  of  the 
multipolar  type,  and  are  frequently  seen  to  give  rise  to  nerve  fibres 
which  emerge  from  the  nerve. 

The  lateral  nerve  is  single  throughout  its  entire  length,  and  no 
trace  of  additional  lateral  nerves,  such  as  have  been  described  in  other 
Cestodes,  has  been  found. 

In  the  posterior  part  of  each  proglottis  the  lateral  nerve  becomes 
enlarged  by  the  aggregation  of  ganglionic  cells,  forming  what  I  have 
called  the  posterior  lateral  ganglion  (PL  22,  Fig.  6  gn.lp).  It  lies 
close  to  the  longitudinal  excretory  tube  (PL  25,  Fig.  28  and  PL  26, 
Fig.  31),  and  nearly  opposite  the  point  whence  the  transverse  ex- 
cretory tube  is  given  off.  The  ganglion  is  ellipsoidal,  its  antero- 
posterior  diameter  being  greater  than  its  dorso-ventral  diameter, 
which,  in  turn,  is  greater  than  its  dextro-sinistral  diameter.  It  varies 
considerably  in  size,  being  largest  in  those  proglottides  which  contain  very 
young  embryos  while  in  the  older  proglottides  it  undergoes  degeneration. 

From  this  ganglion  there  arise  besides  several  smaller  nerves, 
two  large  ones,  one  from  its  dorsal,  the  other  from  its  ventral  surface ; 

Zool.  Jahrb.  XIII.    Abth.  f.  Morph.  25 


376  ,  WM.  L.   TOWEfc, 

these  pass  mediad,  one  above,  the  other  below  the  excretory  tube, 
crossing  the  proglottis  to  the  corresponding  regions  of  the  ganglion 
of  the  opposite  side.  These  two  nerves  are  the  dorsal  and  the  ventral 
commissures  (PL  22,  Figs.  6  and  7  corns,  d  and  corns,  v).  They  are 
loose,  band-like  nerves  flattened  dorso-ventrally,  and  plentifully  sup- 
plied with  ganglionic  cells,  either  singly  or  in  groups,  at  points  where 
nerves  are  given  off.  The  ganglionic  cells  are  almost  always  of  the 
bipolar  type  (PI.  24,  Fig.  20),  but  otherwise  have  the  same  character- 
istics as  the  ganglionic  cells  from  the  other  parts  of  the  nervous 
system.  I  have  not  found  any  binding  cells  along  the  dorsal  com- 
missure, and  from  its  loose  texture  it  is  doubtful  if  any  exist. 
This  nerve  in  its  passage  across  the  proglottis  lies  slightly  behind 
the  transverse  excretory  tube  and  among  the  transverse  muscles, 
some  of  which  frequently  run  through  the  substance  of  the  nerve. 
Because  of  this  peculiarity  the  nerve  is  often  so  broken  up  and  con- 
cealed by  the  bundles  of  muscles  that  it  is  difficult  to  trace  its  course. 
In  places  it  appears  as  a  moderately  compact  nerve,  but  it  nuiy 
shortly  become  a  mere  tangle  of  nerve  and  muscle  fibres,  from  which 
it  may  emerge  as  a  broad  sheet  of  nervous  tissue.  This  nerve  is 
inconstant  in  form,  like  all  the  nerve  structures  excepting  those  of 
the  scolex  and  the  lateral  nerves.  Its  inconstancy  of  form  is  due,  I 
believe,  to  the  fact  that  the  nerve  elements  lie  embedded  in  the  tissues 
of  the  body  without  any  protective  structure  to  bind  them  into  a 
compact  nerve. 

From  the  outer  edge  of  the  posterior  lateral  ganglion  there 
arises  a  cluster  of  nerve  fibres,  the  largest  and  most  important  of  which 
is  the  marginal  nerve  (n.  marg).  This  arises  from  the  anterior  portion 
of  the  outer  edge  of  the  ganglion,  passes  outward  and  then  anteriad 
through  the  greater  part  of  the  margin  of  the  proglottis  (PL  22, 
Fig.  6,  PL  23,  Fig.  12).  A  short  thick  nerve  arises  from  the  posterior  outer 
edge  of  the  ganglion,  and  passes  posteriad  into  the  proglottis,  which 
lies  immediately  behind  that  in  which  the  ganglion  is  located.  A 
cluster  of  still  shorter  branching  nerves  arises  from  the  lateral  margin 
of  the  ganglion  between  the  marginal  and  the  posterior  nerves  and 
is  distributed  to  the  outer  posterior  angle  of  the  proglottis. 

The  posterior  lateral  ganglion  is  made  up  of  a  mass  of  ganglionic 
cells  and  a  great  number  of  nerve  fibres  intermingled  in  a  most 
confusing  manner.  Transverse  sections  of  the  proglottis  in  the 
plane  of  the  dorsal  and  ventral  commissures  (PL  25,  Fig.  28  and 
PL  26,  Fig.  31)  are  the  most  instructive,  although  frontal  sections 


the  nervous  system  in  the  Cestode  Moniezia  expansa.  377 

(PL  21,  Fig.  3),  are  nearly  as  good.  The  nerve  fibres,  on  passing 
into  and  out  of  the  ganglion,  pursue  almost  every  possible  direction, 
making  a  tangle  that  I  have  not  been  able  to  unravel;  yet  there 
appear  to  be  certain  paths  within  the  ganglion  that  are  recognizable, 
owing  to  the  number  of  nerve  fibres  which  take  the  same  direction. 
The  ganglionic  cells  associated  with  the  nerve  fibres  appear  in  Fig.  28 
(PL  25)  and  Fig.  31  (PL  26)  to  be  of  a  rounded  form,  but  they  are  in 
reality  multipolar,  since  they  each  possess  numerous  protoplasmic  pro- 
cesses. Isolated  cells  from  this  ganglion  are  shown  in  Figs.  16  and 
17  (PL  24)  more  highly  magnified.  Two  kinds  of  these  nerve  cells 
may  perhaps  be  recognized,  differing  in  size  and  in  the  richness  of 
their  branching;  those  which  lie  in  the  center  of  the  ganglion  are 
larger  and  more  richly  branched,  while  those  at  the  periphery  are 
smaller,  usually  bipolar,  and  less  richly  branched.  Otherwise  the  cells 
are  alike.  The  nucleus  is  rather  small,  compared  with  the  nucleus  of 
a  ganglionic  cell  of  the  scolex,  and  hyaline,  and  it  contains  a  deeply 
staining  nucleolus.  In  some  cases  under  a  very  high  magnification  a 
faint  chromatic  reticulum  may  be  seen  in  the  nucleus.  The  nuclear 
membrane  is  very  thin,  with  no  observed  thickenings,  and  shows  no 
such  wrinkles  as  are  often  seen  in  the  scolex.  The  coarsely  granular 
cytoplasm  is  gathered  into  a  mass  about  the  nucleus,  from  which  films 
and  threads  of  similar  appearance  radiate  through  the  more  finely 
granular  cytoplasm  that  occupies  the  periphery  of  the  cell.  Therefore 
these  cells  invariably  have  a  stellate  appearance. 

There  are  also  ganglionic  cells  that  lie  just  outside  the  ganglion 
and  send  their  nerve  fibres  for  the  most  part  into  the  ganglion.  These 
cells  are  usually  multipolar,  possessing  a  few  dendritic  processes. 
The  nucleus  is  small,  with  a  large,  deeply-staining  nucleolus  (PL  24, 
Fig.  16),  and  very  frequently  a  well  developed  chromatic  reticulum. 
The  cytoplasmic  contents  present  the  usual  stellate  appearance.  I 
have  not  yet  found  in  the  posterior  lateral  ganglion  of  the  mature 
proglottides  any  of  the  richly  branched  binding  cells  found  in  the 
younger  proglottides.  Either  they  are  not  present  (which  I  can  hardly 
believe),  or,  more  likely,  VOM  RATH'S  method  will  not  differentiate 
them  sufficiently  in  the  mature  specimens. 

Upon  the  lateral  nerve,  at  about  the  point  where  it  crosses  the 
sexual  ducts  in  their  passage  to  the  gonopore,  there  is  another  ganglionic 
enlargement  --  the  anterior  lateral  ganglion  (gn.l.a,  PL  22,  Fig.  6, 
PL  23,  Fig.  12).  This  is  a  dorsal  enlargement  of  the  lateral  nerve 
due  to  the  accumulation  of  ganglionic  cells  at  that  point  (PL  26, 

25* 


378  WM.   L.   TOWER, 

Fig.  33),  as  in  the  case  of  the  larger  posterior  lateral  ganglion.  In 
structure  it  is  like  the  posterior  lateral  ganglion ,  being  composed  of 
a  number  of  ganglionic  cells  embedded  in  a  matrix  of  nerve  fibres, 
and  the  ganglionic  cells  are  in  every  respect  like  those  of  the  posterior 
lateral  ganglion.  From  the  dorsal  surface  of  the  anterior  ganglion 
there  arise,  sometimes  as  a  single  trunk,  two  nerves  which  pass 
medianward  and  dorsad  and  soon  divide.  One  nerve  passes  laterad, 
becoming  the  external  genital  nerve  (n.  gen.  ex),  and  is  distributed  to 
the  region  of  the  gonopore;  the  other  passes  inward,  becomes  the 
internal  genital  nerve  (n.gen.i,  PL  22,  Fig.  6;  PL  23,  Fig.  12; 
PL  26,  Fig.  33;  PL  24,  Fig.  27),  and  is  distributed  to  the  ovaries, 
uterus,  and  other  sexual  organs  of  the  region.  There  are  a  few 
ganglionic  cells  along  the  course  of  these  nerves,  but  no  binding  cells. 
As  far  as  I  was  able  to  discover  the  anterior  lateral  ganglion  does 
not  become  apparent  until  the  proglottis  is  nearly  mature,  although 
the  two  nerves  are  found  in  younger  proglottides.  This  is  due  pro- 
bably to  the  increased  activity  of  those  parts  upon  reaching  sexual 
maturity. 

There  is  a  ventral  commissure  (PL  22,  Figs.  6  and  7  corns,  v), 
connecting  the  ventral  surfaces  of  the  posterior  lateral  ganglia  of 
each  proglottis,  and  corresponding  in  size,  shape  and  relations  to  the 
dorsal  commissure.  These  two  commissures,  together  with  the  posterior 
lateral  ganglia,  form  a  complete  nerve  ring,  embracing  the  two  longi- 
tudinal excretory  tubes,  and  uniting  the  lateral  nerve  of  one  side 
with  its  fellow  of  the  opposite  side.  These  two  commissural  nerves 
are  united  to  each  other  by  means  of  two  dorso-ventral  connectives. 
These  connectives  have  the  form  of  a  loose  band  of  nerve  fibres  that 
passes  dorso-ventrally  from  one  commissure  to  the  other  close  to 
the  median  surface  of  the  longitudinal  excretory  tube,  and  just  behind 
the  union  of  the  longitudinal  and  transverse  excretory  tubes  (corft.  d-v, 
PL  22,  Figs.  6,  7;  PL  25,  Fig.  28;  PL  26,  Fig.  31).  One  of  these  con- 
nectives with  a  small  part  of  each  of  two  commissures  and  the  cor- 
responding posterior  lateral  ganglion  forms  a  complete  ring  of  nerve 
tissue  that  encircles  the  longitudinal  excretory  tube  immediately  behind 
the  transverse  excretory  tube.  This  dorso-ventral  connective  is  like 
the  commissures  in  structure,  being  a  band  of  loosely  united  nerve 
fibres  associated  with  a  greater  or  less  number  of  ganglionic  cells. 
A  few  nerve  fibres  are  seen  to  pass  off  from  these  connectives,  but  I 
have  not  been  able  to  trace  them  to  their  terminations. 

The  marginal  nerve  (PL  22,  Fig.  6  n.marg),  arises  from  the  an- 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  379 

terior  outer  edge  of  the  posterior  lateral  ganglion,  passes  outward 
for  a  short  distance,  and  then  turning  passes  forward  through  about 
three-fourths  of  the  length  of  the  proglottis;  but  in  no  examples 
that  I  have  seen  is  it  continuous  through  the  whole  of  the  proglottis, 
as  stated  by  COHN  (1897)  for  Taenia.  In  my  preparations  the 
branches  of  the  marginal  nerve  are  distributed  to  the  margin  of  the 
posterior  three-fourths  of  the  proglottis  (PL  23,  Fig.  12),  only  a  few 
fibres  indeed  reaching  as  far  forward  as  the  anterior  fourth.  The  fibres 
from  the  short,  posteriorly  directed  marginal  nerve  ennervate  the 
greater  part  of  the  margin  of  the  anterior  fourth  of  the  next  following 
proglottis,  but  I  was  not  able  to  find  any  branches  that  extended  far 
enough  backward  to  meet  the  fibres  of  the  long  marginal  nerve.  It 
is  of  course  possible,  in  view  of  the  great  variability  of  the  peripheral 
nerves  of  the  parasites,  that  there  may  be  cases  where  the  marginal 
nerve  is  continuous  and  well-marked  throughout  the  entire  length  of 
the  proglottis,  but  I  have  not  yet  seen  such  a  case.  The  structure 
of  the  marginal  nerve  is  shown  in  PL  22,  Fig.  10.  Nerve  fibres  are 
given  off  on  all  its  sides  and  at  frequent  intervals,  and  there  are 
numerous,  spindle-shaped  ganglionic  cells  along  its  course. 

The  two  dorsal  and  two  ventral  nerves  discovered  by  NIEMIEC  in 
the  scolex  and  neck  region  of  Taenia,  are  easily  demonstrated  in  the 
younger  proglottides  (PL  21,  Fig.  1),  and  in  some  cases,  at  least, 
exist  in  the  mature  proglottides  as  well-defined  nerves  with  the 
elements  closely  gathered  together.  These,  which  I  have  described  and 
figured  in  an  earlier  paper,  are  also  represented  in  the  diagrammatic 
Figs.  1  (PL  21),  6,  7  (PL  22),  12  and  13  (PL  23).  It  must  not  be  sup- 
posed, however,  that  these  nerves  always  appear  with  the  same  diagram- 
matic clearness,  for  it  is  only  in  exceptional  cases  that  they  are  so  well 
defined.  In  the  greater  number  of  specimens  examined  these  nerves 
had  become  a  loose,  ill-defined  band  of  tissue  lying  in  the  layer  of  the 
longitudinal  muscles,  with  which  the  nerve  is  closely  associated.  In 
my  earlier  paper  I  have  called  these  nerves  dorsal  and  ventral  con- 
nectives, but  I  am  now  satisfied  that  they  are  continuous  throughout 
the  entire  length  of  the  animal,  and  are  therefore  equivalent  to  the 
four  nerves  of  NIEMIEC.  These  nerves  pass  through,  or  are  closely 
associated  with,  the  dorsal  and  ventral  commissures  of  each  proglottis. 
At  the  place  of  crossing  the  two  form  a  loose  mass  of  nerve  fibres 
with  an  increased  number  of  ganglionic  cells.  These  crossings  I  have 
previously  designated  as  ganglia,  and  have  named  them  according  to 
their  position  in  the  proglottis.  I  have  continued  that  nomenclature  in  the 


380  WM.   L.   TOWER, 

present  paper,  though  it  may  be  an  open  question  whether  the  slight 
accumulation  of  ganglionic  cells  in  these  regions  warrants  giving  them 
the  dignity  of  ganglia.  However,  in  those  cases  where  the  nerve 
elements  are  compacted,  these  ganglia  present  a  structure  not  unlike 
that  of  the  other  ganglia  of  the  nervous  system. 

The  dorsal  and  ventral  longitudinal  nerves  give  off  lateral  branches 
along  their  entire  length,  which  lie  in  the  layer  of  the  longitudinal 
muscles.  Fig.  14  (PI.  23)  shows  one  of  these  nerves  (the  right  dorsal) 
which  is  more  compact  than  usual.  In  the  region  of  the  two  branches 
there  are  ganglionic  cells. 

It  gives  me  pleasure  to  acknowledge  my  indebtedness  to  the 
director  of  the  Zoological  Laboratory,  Dr.  E.  L.  MARK,  for  his  kindly 
critericism  and  many  helpful  suggestions  given  me  during  the  progress 
of  my  work. 

Cambridge,  Mass.,  Sept.  1,  1897. 


Postscript.  Since  this  paper  was  written  COHN  (in  :  Zool.  Jahrl>., 
V.  12,  Anat,  1899,  p.  425—76),  has  published  his  studies  on  the 
nervous  system  of  several  Cestodes.  He  believes  that  all  of  the 
longitudinal  nerves,  together  with  their  transverse  connections  in 
both  scolex  and  proglottides,  constitute  the  central  nervous  system. 
The  branches  from  these  to  the  various  organs  and  to  the  surface  of 
the  animal  he  regards  as  the  peripheral  system. 

From  the  conditions  that  I  have  found  in  Moniezia  I  believe 
this  division  to  be  justifiable,  and  that  there  is  a  true  central  nervous 
system  in  Cestodes.  I  do  not,  however,  agree  with  CORN'S  view  that 
the  "main  commissure"  is  a  mere  connective.  I  find  in  Moniesia  that 
there  is  a  well  developed  pair  of  central  ganglia  in  the  scolex.  These 
ganglia  possess  ganglionic  cells  which  send  nerve  fibres  to  other  parts 
of  the  nervous  system  of  the  scolex,  and  posteriorly  to  the  proglottides. 

Since  this  paper  was  written  I  have  studied  further  the  nervous 
system  of  Cestodes,  using  with  some  success  methylen-blue  and  GOLGI 
impregnations.  I  find  a  distinct  central  system  in  the  scolex,  which 
I  think  may  function  as  a  central  coordinating  center  —  a  brain.  The 
rest  of  the  central  nervous  system  is  comparable  to  a  longitudinal 
nerve  chain.  The  conclusions  reached  in  this  paper  as  to  the  paths 
taken  by  the  fibres  in  the  cephalic  ganglion  were  substantiated  by 
my  more  recent  methylen-blue  and  GOLGI  preparations. 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  381 

Unfortunately  all  my  drawings  and  preparations  were  lost  in  a 
fire  which  occurred  in  March  1898,  and  I  have  not  since  been  able 
to  return  to  the  subject. 

Cambridge,  Mass.,  U.S.A.,  Dec.  14,  1899. 


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382 


WM.   L.   TOWER, 


Explanation  of  Plates. 

Plate  21—26. 


Abbreviations. 


a  anterior 

act  acetabulum 

cl.gn  ganglionic  cell 

cl.  vin  binding  cell 

CO  body  of  cephalic  ganglion 

corns      commissure      of      cephalic 

ganglion 

corns,  d   dorsal  commissure  of  pro- 
glottis 

corns  d'  dorsal  cephalic  commissure 
corns,  v  ventral  commissure  of  pro- 
glottis 

corns,  v'  ventral  cephalic  commissure 
con't.  cep.  dx   right   connective   be- 
tween the  cephalic   and  the  an- 
terior ganglia 

con't.  d-v    dorso-ventral    connective 
conu.  a    anterior    horn    of  cephalic 

ganglion 
conu.  ex    external  horn  of  cephalic 

ganglion 
eta  cuticula 
d  dorsal 
gn.  a.  dx-d     anterior    dextro-dorsal 

ganglion 
gn.  a.  s-v    anterior    sinistro-ventral 

ganglion 

gn.dx  right  cephalic  ganglion 
gn.dx-d  dextro-dorsal  ganglion 
gn.dx-v  dextro-ventral  ganglion 
gn.  I.  a  anterior  lateral  ganglion 
gn.  l.p  posterior  lateral  ganglion 


gn.  s  left  cephalic  ganglion 

gn.s-d  sinistro-dorsal  ganglion 

gn.  s-v  sinistro-ventral  ganglion 

n.  a  anterior  nerve  ring 

n.  gen.  ex  external  genital  nerve 

n.gen.i  internal  genital  nerve 

n.l  lateral  nerve 

n.  Ig.  dx-d  dextro-dorsal  longitudinal 

nerve 

n.  Ig.  dx-v      dextro  -  ventral     longi- 
tudinal nerve 
n.  Ig.  s-d  sinistro-dorsal  longitudinal 

nerve 
n.  Ig.s-v  sinistro-ventral  longitudinal 

nerve 

n.marg  marginal  nerve 
p  posterior 
ut  uterus 
v  ventral 
va.dx    right    arm    of  the    anterior 

loop  of  excretory  tube  in  scolex 
va.  dx-d  dextro-dorsal    longitudinal 

excretory  tube 
va.  dx-v  dextro-ventral  longitudinal 

excretory  tube 

va.  Ig  longitudinal  excretory  tube 
va.s-d   sinistro-dorsal   longitudinal 

excretory  tube 
va.s-v  sinistro-ventral  longitudinal 

excretory  tube. 
va.  t  transverse  excretory  tube 


The  nervous  system  in  the  Cestode  Moniezia  expansa.  383 

Plate  21. 
Figs.  1,  2,  4  and  5  are  diagrammatic. 

Fig.  1.  Reconstruction  of  the  nervous  system  in  the  scolex  ot 
Moniezia  expansa. 

Fig.  2.  Transverse  section  of  the  scolex  at  the  region  /?/?'  (Fig.  1), 
showing  the  position  of  the  nerve  structures. 

Fig.  3.  Frontal  section  through  the  posterior  lateral  ganglion. 
From  a  VOM  RATH  preparation.  X  ^00. 

Fig.  4.  Transverse  section  of  the  scolex  at  the  region  aa1  (Fig.  1), 
showing  the  position  of  the  nerve  structures  etc.  (n.l.dx-d  should  be 
n.  Ig.  dx-d). 

Fig.  5.  Transverse  section  of  the  scolex  at  the  region  yy'  (Fig.  1), 
showing  the  position  of  the  nerve  structures,  etc.  at  that  level. 

Plate  22. 

Fig.  6.  Diagrammatic  reconstruction  of  the  nervous  system  in 
four  proglottides. 

Fig.  7.  Transverse  section  of  a  proglottis  through  the  posterior 
lateral  ganglion  (diagrammatic). 

Fig.  8.  Diagrammatic  representation  of  the  paths  taken  by  the 
nerve  fibres  that  enter  and  leave  the  cephalic  ganglia  (see  p.  371). 

Fig.  9.  Parasagittal  section  through  the  longitudinal  nerve  in  a 
region  between  the  posterior  and  anterior  lateral  ganglia,  showing 
''binding"  cells  and  ganglionic  cells  lying  along  the  nerve.  From  a 
VOM  RATH  preparation.  X  500.  (vt  by  mistake  for  ut.) 

Fig.  10.  Parasagittal  section  of  the  marginal  nerve,  showing  nerve 
fibres  passing  off  from  it.  VOM  RATH  preparation.  X  1100. 

Fig.  11.  Section  (transverse  to  the  chief  axis  of  the  scolex), 
through  the  dorsal  cephalic  commissure,  showing  bipolar  ganglionic  cells. 

Plate  23. 

Fig.  12.  Portion  of  a  diagrammatic  transverse  section  of  a  pro- 
glottis  through  the  anterior  lateral  ganglion  and  the  genital  nerves, 
showing  the  distribution  of  the  nerve  fibres  from  the  marginal  nerve, 
and  from  the  sinistro-dorsal  and  the  sinistro-ventral  longitudinal  nerves. 

Fig.  13.  Parasagittal  section  (diagrammatic),  of  a  proglottis  through 
the  sinistro-dorsal  and  the  sinistro-ventral  longitudinal  nerves,  showing 
distribution  of  the  nerve  fibres. 

Fig.  14.  Portion  of  a  frontal  section  of  a  proglottis  through  a  branch 
of  the  dextro-dorsal  longitudinal  nerve.  VOM  RATH'S  preparation.  X  1000- 

Plate   24. 

Fig.  15.  A  frontal  section  of  the  lateral  nerve  showing  ganglionic 
and  binding  cells.  VOM  RATH.  X  70°- 

Fig.  16.  Portion  of  a  transverse  section  of  a  posterior  lateral 
ganglion,  showing  protecting  ("binding")  cells  upon  the  surface  of  the 


384         WM-  L-  TOWER,  The  nervous  system  in  the  Cestode  Moniezia  expansa. 

ganglion  and  two  ganglionic  cells  that  send  nerve  fibres  (in  another 
plane)  into  the  ganglion.  VOM  BATH  preparation.  X  1500. 

Fig.  17.  A  bipolar  ganglionic  cell  from  the  posterior  lateral 
ganglion.  VOM  RATH.  X  1450. 

Fig.  18.  A  multipolar  ganglionic  cell  from  the  cephalic  ganglion. 
VOM  RATH.  X  1500. 

Fig.  19.  A  bipolar  ganglionic  cell  from  the  cephalic  ganglion. 
VOM  RATH.  X  1450. 

Fig.  20.  A  bipolar  ganglionic  cell  from  the  posterior  lateral 
ganglion.  VOM  RATH.  X  1450. 

Figs.  21  and  22.  Unipolar  ganglionic  cells  from  the  anterior 
ganglia.  VOM  RATH.  X  1450. 

Figs.  23  and  24.  Bipolar  ganglionic  cells  from  the  anterior  ganglia. 
VOM  RATH.  X  145°- 

Fig.  25.  A  neuron  from  the  lateral  nerve  in  the  neck  region. 
VOM  RATH.  X  1500. 

Fig.  26.  A  unipolar  ganglionic  cell  from  the  anterior  dorso-dextral 
ganglion.  VOM  RATH.  X  1450. 

Fig.  27.  Frontal  section  of  the  anterior  lateral  ganglion  and 
genital  nerves.  VOM  RATH.  X 


Plate  25. 

Fig.  28.  Transverse  section  through  the  posterior  lateral  ganglion. 
VOM  RATH.  X  80°. 

Fig.  29.  Protecting  cell  as  seen  on  lateral  nerve.  VOM  RATH. 
X  800. 

Fig.  30.  Dorso-ventral  longitudinal  section  through  lateral  nerve 
showing  protecting  and  ganglionic  cells.  VOM  RATH.  X  1000. 

Plate  26. 

Fig.  31.  Transverse  section  of  the  posterior  lateral  ganglion.  VOM 
RATH.  X  80°. 

Fig.  32.  Frontal  section  of  the  posterior  lateral  ganglion  in  the 
"neck"  region.  VOM  RATH.  X  90°- 

Fig.  33.  Frontal  section  through  the  anterior  lateral  ganglion. 
VOM  RATH.  X  80°- 


Zoolog.  JahrbucherBd.  IJ.Abth.f.Morph. 


Taf.21. 


yn.a.dx  d. 


gn.a.s-v 


Tower  gez. 


Yerl  v.Gustav  Fisdier.Jena. 


Lith.Ansi.v.J.ArndtJena. 


ZoologJahrbiicherBd.  13  Ablhf.  Morpk. 


Taf.22. 


Tower  gez. 


Verl.v  Gustav  Fischer,  Jena. 


LithAnst.vJ.Arndt.Jena. 


Zoolog.Jahrbiicher  Bd.13.  Ablh.  f.  Morph. 


Taf.ZJ. 


Tower 


VerLv.Gustav  Fischer,  Jena. 


Lith.Anst.vJ.Arndt.JeRa. 


/oolog.JahrbiichtrBd.ti.Abttif.Morph. 


Taf.24-. 


Tower  gez. 


Verb.  Gustav  Fischer,  Jena. 


Lith.Anst.vJ.Arndt.Jena. 


Zoolog.  Jahrbiicher  Bd.  13.  Abthf.Morph. 


Taf.?j. 


r 


28. 


con,  t.d-v.  - 


/ 


.10. 


/ 

at. 


civi.n. 


Verl.v.  Gustav  FischerJena 


29. 


. 


Zoolog.  JahrbiiclurBd.  ll.Abthf.Morph. 


Taf.26. 


.'a. ly. 


conl.d-v. 


— n.gcn.i. 


ri.qcn.ejc.    • 


(fn.La. 


Verl  v.Guslav  Fischer.Jena. 


Lith.Anst.v.J.ArndtJena. 


CONTRIBUTIONS  FROM  THE  ZOOLOGICAL  LABORATORY  OP 
THE  MUSEUM  OF  COMPARATIVE  ZOOLOGY  AT  HARVARD 
COLLEGE. 

E.  L.  MARK,  Director. 


***  Abbreviations  used  :  — 

B.  M.  C.  Z for  Bull.  Mus.  Comp.  Zob'l. 

P.  A.  A for  Proceed.  Auier.  Acad.  Arts  and  Sci. 

P.  B.  S.  N.  II for  Proceed.  Bost.  Soc.  Nat.  Hist. 

1.  BARNES,  W.  —  On  the  Development  of  the  Posterior  Fissure  of  the  Spinal  Cord,  and 

the  Reduction  of  the  Central  Canal,  in  the  Pig.    P.  A.  A.  19  :  97-110.    3  pis.  1884. 

2.  TUTTLB,  A.  H.  —  The  Relation  of  the  External  Meatus,  Tympanum,  and  Eustachian 

Tube  to  the  First  Visceral  Cleft.    P.  A.  A.  19  :  111-132.    2  pis.    1884. 

3.  ATEBS,  H.  — On  the  Development  of  Oecanthus  niveus  and  its  Parasite,  Teleas. 

Mem.  Bost.  Soc.  Nat.  Hist.  S  :  225-281.    8  pis.    Jan.,  1884. 

4.  WHITMAN,  C.  O.  — The  External  Morphology  of  the  Leech.    P.  A.  A.  2O  :  76-87. 

1  pi.    Sept.,  1884. 

5.  PATTEN,  W.  —  The  Development  of  Phryganids,  with  a  Preliminary  Note  on  the 

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20  :  88-106.    3  pis.     Oct.,  1884. 

7.  FAXON,  W.  — Descriptions  of  New  Species  of  Cambarus;   to  which  is  added  a 

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13  :  247-258.    2  pis.    Jun.,  1888. 

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B.  M.  C.  Z.  17  :  171-190.    2  pis.    Jul.,  1889. 

15.  MARK,  E.  L.  — Studies  on  Lepidosteus.     Parti.     B.  M.  C.  Z.  19:  1-127.     9  pis. 

Feb.,  1890. 

16.  EIGENM ANN,  C.  II.  —  On  the  Egg  Membranes  and    Micropyle  of  some  Osseous 

Fishes.     B.  M.  C.  Z.  19:  129-154.     3  pis.    Mar.,  1890. 

17.  PARKER,  G.  II.  — The  Histology  and    Development  of  the  Eye  in  the  Lobster. 

B.  M.  C.  Z.  2O  :  1-60.    4  pis.     May,  1890. 

18.  AYERS,  H.  —  The  Morphology  of  the  Carotids,  based  on  a  Study  of  the  Blood-vessels 

of  Chlamydoselachus  anguineus,  Garman.    B.  M.  C.  Z.  IT  :  191-223.    1  pi.    Oct., 

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the  Colony.    B.  M'.  C.  Z.  2O  :  101-151.    11  pis.    Nov.,  1890. 

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21.  HENCHMAN,  ANNIE  P.  —  The  Origin  and  Development  of  the  Central  Nervous  Sys- 

tem in  Limax  inaximus.    B.  M.  C.  Z.  30 :  169-208.    10  pis.    Dec.,  1890. 

22.  HITTER,  W.  E.  —The  Parietal  Eye  in  some  Lizards  from  the  Western  United  States. 

B.  M.  C.  Z.  80 :  209-228.    4  pis.    Jan.,  1891. 

23.  DAVENPORT,  C.  B.  — Preliminary  Notice  on  Budding  in  Bryozoa.    P.  A.  A.  35: 

278-282.    Mar.,  1891. 

24.  WOODWORTH,  W.  M.  — Contributions  to  the  Morphology  of  theTurhellaria.  — I.  On 

the  Structure  of  Phagocata  gracilis,  Leidy.    B.  M.  C.  Z.  81 :  1-44.    4  pis.    Apr., 
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25.  PARKER,  G.  II.  — The  Compound  Eyes  in  Crustaceans.    B.  M.  C.  Z.  ai :  45-142. 

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26.  WARD,  II.  B.  — On  some  Points  in  the  Anatomy  and  Histology  of  Sipunculus 

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27.  FIELD,  II.  II.  — The  Development  of  the  Prouephros  and  Segmental  Duct  in  Am- 

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28.  DAVENPORT,  C.  B.  —  Observations  on  Budding  in  Paludicella  and  some  other  Bryo- 

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the  Pectoral  Fin.    B.  M.  C.  Z.  83  :  91-134.    8  pis.    Apr.,  1892. 

82.  WARD,  II.  B.  — On  Nectonema  agile.    B.  M.  C.  Z.  83  :  135-188.    8  pis.    Jun.,  1892. 

33.  DAVENPORT,  C.  B.— On  Urnatella  gracilis.    B.  M.  C.  Z.  84:  1-44.     6  pis.    Jan., 

1893. 

34.  DAVENPORT,  C.  B.  —  Note  on  the  Carotids  and  the  Ductus  Botalli  of  the  Alligator. 

B.  M.  C.  Z.  84  :  45-50.    1  pi.    Jan.,  1893. 

35.  KITTKH,  W.  E.  — On  the  Eyes,  the  Integumentary  Sense  Papillae,  and  the  Integu- 

ment of  the  San  Diego  Blind  Fish  (Typhlogobius  californiensis,  Steindachner). 
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36.  NK  K  KK-.ON.  W.  S.  — The  Development  of  the  Scales  in  Lepidosteus.    B.  M.  C.  Z. 

84  :  115-140.    4  pis.    Jul.,  1893. 

37.  DAVENPORT,  C.  B.  —  Studies  in  Morphogenesis. —I.   On  the  Development  of  the 

Cerata  in  ^Eolis.    B.  M.  C.  Z.  84  :  141-148.    2  pis.    Jul.,  1893. 

38.  WOODWORTH,  W.  McM.  —  A  Method  of  Orienting  •mall  Objects  for  the  Microtome. 

B.  M.  C.  Z.  85  :  45^7.    Dec.,  1893. 

39.  KOPOID,  C.  A.  — On  some  Laws  of  Clearftfe  in  Limax.     P.  A.  A.  8O:   180-203. 

2  pis.     1894. 

40.  DAVENPORT,  C.  B.  — Studies,  etc.  — II.   Regeneration  in  Obelia  and  its  Bearing  on 

Differentiation  in  the  Germ-Plasma.    Anat.  Anz.  » :  283-294.    6  figs.    Feb.  15, 
1894. 

41.  HOLBROOK,  A.  T.  —  The  Origin  of  the  Endocardium  in  Bony  Fishes.    B.  M.  C.  Z. 

85:75-97.    5  pis.    Aug.,  1894. 

42.  CASTLE,  W.  E.  —  On  the  Cell  Lineage  of  the  Ascidian  Egg.    A  Preliminary  Notice. 

P.  A.  A.  3O  :  200-216.    2  pis.    Oct.,  1894. 

43.  WEYSSE,  A.  W.  — On  the  Blastodermic  Vesicle  of  Sus  scrofa  domesticus.    P.  A.  A. 

30:283-323.    4  pis.     Dec.,  1894. 

44.  WILCOX,  E.  V.  — Spermatogenesis    of    Caloptenus    fernur-rubrum.       Preliminary 

Notice.    Anat.  Anz.  1C  :  303,  304.    Dec.  19, 1894. 

45.  MILLER,  GERRIT  S.,  JR. —  On  the  Introitus  Vaginse  of  certain  Muridse.   P.  B.  S.  N.  H. 

86  :  459-468.     1  pi.    Feb.,  1895. 

46.  DAVBNPORT,  C.  B.,  AND  CASTLE,  W.  E.  — Studies,  etc.  — III.  On  the  Acclimatiza- 

tion of  Organisms  to  High  Temperatures.     Arch.  f.  Entwickelungsmechauik  8  : 
227-249.    Jul.  23, 1895. 

47.  WILCOX,  E.  V.  —  Spermatogenesis  of  Caloptenus  femur-rubrum  and  Cicada  tibicen. 

B.  M.  C.  Z.  87  :  1-32.    5  pis.  -May,  1895. 

48.  KOPOID,  C.  A.  — On  the  Early  Development  of  Limax.    B.  M.  C.  Z.  87  :  33-118. 

8  pis.    Aug.,  1895. 


49.  NICKERSON,  W.  S.  —  On  Stichocotyle  nepliropis  Cunningham,  aParasite  of  the  Ameri- 

can Lobster.    Zool.  Jahrb.,  Abtli.  f.  Anat.  8  :  447-480.    3  pis.    1895. 

50.  DAVENPORT,  C.  B.  —  Studies,  etc.  —  IV.  A  preliminary  Catalogue  of  the  Processes 

concerned  in  Ontogeny.    B.  M.  C.  Z.  27  :  171-199.    31  figs,  in  text.    Nov.,  1895. 

51.  PARKER,  G.  II.,  AND  FLOYD,  R.  —  The  Preservation  of  Mammalian  Brains  by  Means 

of  Forinol  and  Alcohol.    Anat.  Anz.  11 :  156-158.    Sept.  28,  1895. 

52.  CASTLE,  W.  E.  —  The    Early    Embryology    of  Ciona  intestinalis,  Flemming  (L.). 

B.  M.  C.  Z.  27  :  201-280.  "  13  pis.    Jan.,  1896. 

53.  DAVENPORT,  C.  B.,  AND  NEAL,  H.  V.  —  Studies,  etc.  —  V.  On  the  Acclimatization 

of  Organisms  to  Poisonous  Chemical  Substances.    Arch.  f.  Entwickelungsme- 
chanik  2  :  564-583.    3  figs.    Jan.  28,  1896. 

54.  PARKER,  G.  H.,  AND  FLOYD,  R. —  Formaldehyde,  Formaline,  Formol,  and  Forma- 

lose.    Anat.  Anz.  11 :  567,  568.    Feb.  14,  1896. 

55.  PARKER,  G.  H. — The   Reactions  of  Metridium  to  Food  and    other    Substances. 

B.  M.  C.  Z.  29 :  105-119.    Mar.,  1896. 

56.  GEROULD,  J.  H.  — The     Anatomy    and    Histology    of    Caudina     arenata     Gould. 

P.  B.  S.  N.  H.  27:   7-74.    8  pis.  and  B.  M.  C.  Z.  29:   121-190.     8  pis.      Apr., 
1896. 

57.  PARKER,  G.  H.  —  Variations  in  the  Vertebral  Column-  of  Necturus.    Anat.  Anz.  11 : 

711-717.     2  figs.    Mar.  29,  1896. 

58.  WILCOX,  E.  V. — Further  Studies  on  the   Sperinatogenesis  of  Caloptenus  femur- 

rnbrum.     B.  M.  C.  Z.  29  :  191-206.     3  pis.    Jun.,  1896. 

59.  MAYER,  A.  G.  — The  Development  of  the  Wing  Scales  and  their  Pigment  in  Butter- 

flies  and  Moths.    B.  M.  C.  Z.  29 :  207-236.    7  pis.    Jun.,  1896. 

60.  FOLSOM,  J.  W.  —  Neelus  murinus,  representing  a  new  Thysanuran  Family.    Psyche, 

7  :  391,  392.    1  pi.    Jun.,  1896 

61.  GOTO,  S.  —  Vorlaufige  Mittheilung  Uber  die  Entwicklung  des  Seesternes  Asterias 

pallida.    Zool.  Anz.  19  :  271-273.    Jun.  15,  1896. 

62.  PARKER,  G.  H.  —Pigment  Migration  in  the  Eyes  of  Palaemonetes.    A  Preliminary 

Notice.    Zool.  Anz.  19  :  281-284.    2  figs.    Jun.  29, 1896. 

63.  WOODWORTH,  W.  McM.  — Preliminary  Report  on  Collections  of  Turbellaria  from 

Lake  St.  Clair  and  Charlevoix,  Michigan.    Bull.  Michigan  Fish  Commission, 
No.  «  :  94,  95.     1896. 

64.  GOTO,  S.  —Preliminary  Notes  on  the  Embryology  of  the  Starfish  (Asterias  pallida) . 

P.  A.  A.  31 :  333-335.    Jul.,  1896. 

65.  WOODWORTH,  W.  McM.  — Report  on  the  Turbellaria  collected  by  the  Michigan 

State  Fish  Commission  during  the  Summers  of  1893  and  1894.    B.  M.  C.  Z.  29 : 
237-244.    1  pi.    Jun.,  1896. 

66.  TOWER,  W.  L.  —  On  the  Nervous  System  of  Cestodes.     Zool.  Anz.  19:  323-327. 

2  figs.    Jul.  20,  1896. 

67.  DAVENPORT,  GERTRUDE  C.  — The  Primitive  Streak  and  Notochordal  Canal  in  Che- 

Ionia.    Radcliffe  Coll.  Monographs,  No.  8,  54  pp.    11  pis.     [Sept.],  1896. 

68.  LEWIS,  MARGARET.  —  Centrosome  and  Sphere  in  Certain  of  the  Nerve  Cells  of  an 

Invertebrate.    Anat.  Anz.  12  :  291-299.    11  figs.    Sept.  2,  1896. 

69.  JUDD,  S.  D.  — Description  of  three  Species  of  Sand  Fleas  (Amphipods)  collected  at 

Newport,  Rhode  Island.    Proc.  U.  S.  Nat.  Mus.  18  :  593-603.    11  figs.    Aug.,  1896. 

70.  JENNINGS,  H.  S.  — The  Early  Development  of  Asplanchna  Herrickii  de  Guerne. 

A  Contribution  to  Developmental  Mechanics.    B.  M.  C.  Z.  3O  :  1-118.    10  pis. 
Oct.,  1896. 

71.  NEAL,  H.  V.  — A  Summary  of  Studies  on  the  Segmentation  of  the  Nervous  System 

in  Squalus  acanthias.    A  Preliminary  Notice.    Anat.  Anz.  12 :  377-391.    6  figs. 
Oct.  20,  1896. 

72.  DAVENPORT,  C.  B.,  AND  CANNON,  W.  B.  — On  the  Determination  of  the  Direction 

and  Rate  of  Movement  of  Organisms  by  Light.    Jour,  of  Physiol.  21 :  22-32. 
1  fig.    Feb.  5,  1897. 

73.  DAVENPORT,  C.  B.,  AND  BULLARD,  C.  — Studies,  etc.  — VI.  A  Contribution  to  the 

Quantitative  Study  of  Correlated  Variation  and  the  Comparative  Variability  of  the 
Sexes.    P.  A.  A.  32  :  87-97.    Dec.,  1896. 


74.  MAYER,  A.  G.  —  On    the    Color    and    Color-Patterns    of  Moths    and    Butterflies. 

B.  M.  C.  Z.  30  :   167-258.     10  pis.     Feb.  [Mar.],  1897  and  P.  B.  8.  N.  II.    27  : 
243-330.    10  pis.     Mar.,  1897. 

75.  PARKER,  G.  H.  —  The  Mesenteries  and   Siphonoglvph*  in  Mctridium  margiuutuiu 

Milne-Edwards.    B.  M.  C.  Z.  3O:  257-272.     1  pi!     Mar.,  1897. 

76.  PARKER,  G.  II.  —  Photomechanical  changes  in  the  Retinal  Pigment  Cells  of  Palae- 

monetes,  and  their  Relation  to  the  Central  Nervous  System.    B.  M.  <  .  /.  :io  : 
273-300.    Ipl.    Apr.,  1897. 

77.  BUNKER,  F.  S.  —  On  the  Structure  of  the  Sensory  Organs  of  the  Lateral  I.iin-  <>f 

Ameiurus  nebulosus  Le  Sueur.     Anat.  Anz.  13 :  256-260.     Mar.  3,  1897. 

78.  WOODWORTU,  W.  McM.  —On  a  Method  of  Graphic  Ki-.-,,u-triii-tH>n  from  s.-i        - 

tions.    Zeit.  f.  wiss.  Mikr.  14  :  15-18.    Jul.,  1897. 

79.  BREWSTER,  E.  T.  — A  Measure  of  Variability,  and  the  Relation  of  Individual  Varia. 

tions  to  Specific  Differences.    P.  A.  A.   39  :  269-280.    May,  1897. 

80.  DAVENPORT,  C.  B.  —  The   Rdle  of  Water  in  Growth.     P.  B.  S.  N.  II.  98:73-84. 

Jun.,  1897. 

81.  LEWIS,  MARGARET.  — Clymene  prodin-ta  sp.  nov.    P.  B.  S.N.  II.  98  :  111-1K.,  •_' pN. 

Aug.,  1897. 

82.  PORTER,  J.  F.  —  Two  new  Grcgarinida.    Jour.  Morph.  14  :  1-20.    3  pis.    Jun.,  1897. 

83.  Woo DWORTH,  W.  McM.  —  Contributions,    etc. —  II.   On    some    Turbellarm    from 

Illinois.    B.  M.  C.  Z.  31 :  1-16.    1  pi.    Oct.,  1897. 

84.  PORTER,  J.  F.  —  Trichonympha,  and  other  Parasite*  of  Tonnes  flavipes.    B.  M .  C.  Z. 

31: :  45-68.     6  pis.    Oct.,  1897. 

85.  WAITE,  F.  C.  — Variations  in  the   Brachial  and   Lumbo-Sacral  Plexi  of  Nerturus 

manilosus  Rafinesque.     B.  M.  C.  Z.  31 :  69-92.     2  pl«.     Nov.,  1897. 

86.  DAVENPORT,  C.  B.,  AND  PERKINS,  HELEN. —  A  Contribution  to  the  Study  of  Geo- 

taxis  iu  the  Higher  Animals.    Jour,  of  Physiol.  99  :  99-110.    Sept.  1,  1897. 

87.  PARKER,  G.  II., AND  TOZIER.C.  H.  — The  Thoracic  Derivatives  of  the  Postcardinal 

Veins  in  Swine.    B.  M.  C.  Z.  31 :  131-144.    5  figs.     Mar.,  1898. 

88.  GOTO,  S. — The  Metamorphosis  of  Asterias  pallida,  with  Special  Reference  to  the 

Fate  of  the  Body  Cavities.    Jour.  Coll.  S<-i.,  Tokyo,  1O  :  239-278.    6  pis.     1898. 

89.  NEAL,  H.  V.  — The  Segmentation  of  the  Nemni*  System   in  Squalus  a. 

A  Contribution  to  the  Morphology  of  the  Vertebrate   Head.    B.  M.  C.  /.  :tl  : 
145-294.    9  pis.    May,  1898. 

90.  LEWIS,  MARGARET.  —  Studies  on  the  Central  and  Peripheral  Nervous  s\-t.ni-of 

two  Polychaete  Annelids.    P.  A.  A.  33  :  22:;-2«8.    8  pis.    Apr.,  1898. 

91.  HAMAKER,  J.  I.  —  The  Nervous  System  of  Nereis  virens  Sars.    A  Study  in  <  ..m- 

parative  Neurology.     B.  M.  C.  Z.  39  :  87-124.    5  pis.    Jun.,  1898. 

92.  FIELD,  \V.  L.  W.  —  A   Contribution  to  the   Study   of  Individual  Variation  in  the 

Wings  of  Lepidoptera.    P.  A.  A.  33  :  389-396.    5  figs.    Jun.,  1898. 

93.  MARK,  E.  L.  —  Preliminary  Report  on  Branchiocerianthus  urceolus,  A  nru  TM>'  «»:' 

Actinian.     B.  M.  C.  Z.  39  :  145-154.    3  pis.    Aug.,  1898. 

94.  SARGENT,  P.  E.  — The  Giant  Ganglion  Cells  in  the  Spinal  Cord  of  Ctenolabrus 

coerueus.    Anat.  Anz.  15;  212-225.    10  figs.    Dec.  20, 1898. 

95.  RAND,  H.  W.  — Regeneration  and  Regulation  in  Hydra  viridis.    Arch.  Entwickel- 

ungsmechanik,  8  :  1-34.    4  pis.    Feb.  21, 1899. 

96.  FOLSOM,  J.  W.  — The  Anatomy  and  Physiology  of  the  Mouth-Parts  of  the  Collem- 

bolan,  Orchesella  cincta  L.    B.  M.  C.  Z.  35  :  5-39.    Jul.,  1899. 

97.  MARK,  E.  L.  —  "  Branchiocerianthus,"  a  Con-ection.      Zool.   Anz.  99:   ^74,   J7  .. 

Jun.  26,  1899. 

98.  BANCROFT,  F.  W.  —  Ovogenesis  in  Distaplia  occidentalis  Ritti-r  (MS.) ,  with  Remarks 

on  Other  Species.    B.  M.  C.  Z.  35  :  57-112.    6  pis.    Oct.,  1899. 

99.  GALLOWAY,  T.  W.  —  Observations    on    Non-sexual    Reproduction    in    Dero    vaga. 

B.  M.  C.  Z.  35  :  113-140.    5  pis.    Oct.,  1899. 

100.  PARKER,  G.  H.  — The  Photomechanical  Changes  in  the  Retinal  Pigment  of  Gain- 

marus.    B.  M.  C.  Z.  35 :  141-148.     1  pi.    Oct.,  1899. 


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